New Zealand is facing pressure to save the world's rarest dolphin at an international scientific meeting underway this week in what conservationists say is a test of the nation's "clean, green" credentials.

The Maui's dolphin, found only in shallow waters off the North Island's west coast, is listed as critically endangered, with just 55 adults remaining and experts fearing it will disappear by 2030 unless urgent action is taken.

The grey and white Maui's, named after a Polynesian demi-god, is one of the world's smallest dolphins, with a maximum length of 1.7 metres (5.5 foot).

Associate professor of zoology at Otago University Liz Slooten said an expert panel appointed by the government estimated last year that five of the dolphins were killed annually as fishing industry "bycatch".

"They are literally teetering in the brink of extinction," Slooten said. "They won't last if we don't do something right now."

The New Zealand government believes that entanglement in gill nets -- vertical mesh nets left in the water for long periods -- is the main cause of death.

Conservation groups say proposals for seabed mining, including seismic surveying, also pose a major threat.

Some restrictions on gill netting and trawling in the dolphins' habitat were introduced last year but the government stopped short of meeting an International Whaling Commission (IWC) call for an immediate ban to save the species.

Instead, it called for submissions to a threat management plan, saying it would assess both the risks facing the dolphins and "the potential impact of this extended ban on the local fishing community".

While submissions for the management plan closed last November, no further action has been taken and critics accuse the government of stalling.

"Time is of the essence, with populations this low, numbers can drop off very rapidly," Greenpeace campaigner Karli Thomas said.

"We're worried the government is delaying to the point of no return for Maui's dolphins. Just waiting for them to drop off the agenda because they're extinct is not solving the problem, that's the loss of a species from the planet."

The issue was due to resurface at a meeting of the IWC scientific committee which opened in South Korea's southern island of Jeju on June 3 and runs until June 15, where delegates were again set to urge Wellington to act.

The local fishing industry disputes allegations it is to blame for the dolphins' demise, saying it has become a convenient scapegoat for environmentalists.

Keith Mawson, who runs a Taranaki fish processing firm, said there had only been one confirmed bycatch fatality in the past 25 years and that may have been a Hector's dolphin, rather than the closely related Maui's.

He said the industry faced annihilation due to research conducted with the sole purpose of limiting fishing, while ignoring other potential causes of death, such as the parasitic disease toxoplasmosis in the dolphins.

"You could exclude fishing right along the west coast of the North Island and it's not going to ensure the survival of this dolphin," he said.

Organisations such as the Society for Marine Mammalogy say evidence about the Maui's plight is "extremely strong" and New Zealand, which has long marketed itself as "100 percent pure", must act quickly if it wants to save the species.

"Scientific advice often involves a degree of uncertainty, but in a situation such as this one, involving a critically endangered sub-species, delay to resolve uncertainty could have dire, irrevocable results," it said in a letter to Prime Minister John Key earlier this year.

Phil McCabe, a tourism operator who has established the environment group Kiwis Against Seabed Mining, said New Zealand's international reputation as an environmental leader was on the line.

"People come to here because of the assumption that we're clean and green, the image we've portrayed," he said.

"If we start knocking out species that we could have saved to make a few bucks it's not going to take long for the world to cotton on."

Slooten said the lack of action also opened up New Zealand to accusations of hypocrisy as it continued to strongly oppose Japanese whaling at forums like the IWC.

"It hasn't gone unnoticed to the Japanese that while we're telling them not to kill Minke whales, of which there are many all around the world, we're not doing much to save our own endangered dolphins," she said.